Configuration of a near-field communication router according to the modulation type

ABSTRACT

A first near-field communication device is configured according to a modulation type transmitted by a second device. A decoder of the first device decodes a received signal using type-A modulation during a first time slot corresponding to the duration of a first type-A symbol. The first device determines the modulation type transmitted by the second device according to the value of the decoded symbol.

BACKGROUND Technical Field

Embodiments generally relate to electronic circuits and, morespecifically, to near-field radio frequency communication devices.

Discussion of the Related Art

More and more radio frequency communication devices are capable ofoperating in near field with a fixed terminal or another mobile device.In particular, most mobile phone type telecommunication devices are nowequipped with a near-field communication (NFC) router.

It is generally spoken of NFC devices operating in card mode (oremulating a card), as opposed to a second operating mode of suchdevices, which is to emulate a card reader to cooperate with anothernear-field device. The device then behaves as a terminal.

There are different near-field communication standards. The differencebetween such standards essentially is the modulation and coding type ofdata to be transmitted. Formerly, transponders were most often dedicatedto one type of modulation. They are now designed to be able to operateaccording to different modulation types are can thus be configured toset this type on each new transaction with a terminal.

The modulation type is most often set by the terminal and thetransponder-type device modifies the configuration of its NFC router tobe able to communicate with this reader.

Usually, the router or the radio frequency front head capable ofoperating according to different modulations successively switches tothese different modulations until it recognizes a request transmitted bya reader. This however takes time.

Further, some terminals are themselves capable of operating according todifferent modulation types to be able to adapt to transponders dedicatedto a single type. In this case, the terminal successively sends requestsaccording to the different types until it receives a response in one ofthe types. However, the terminal should leave enough time between twotypes (generally on the order of a few milliseconds) so that aconfigurable transponder also has time to scan the different modulationtypes until both configurations (terminal and transponder) match.

Such a configuration process is long and makes the device in card moderisk never to detect a request.

BRIEF SUMMARY

An embodiment facilitates addressing all or part of the disadvantages ofusual card-mode near-field telecommunication devices.

An embodiment provides a process for configuring a device in card mode.

An embodiment provides a method for configuring a first near-fieldcommunication device according to a modulation type transmitted by asecond device, wherein:

-   -   a decoder of the first device is configured to decode a type-A        modulation;    -   a signal received during a first time slot corresponding to the        duration of a first type-A symbol is decoded; and    -   the first device is configured according to the value of the        decoded symbol to determine the modulation type.

According to an embodiment, said duration corresponds to the duration ofa bit in type-A modulation.

According to an embodiment, said symbol is divided in four and decodedby assigning a state 0 or 1 to each quarter.

According to an embodiment, if the first symbol is 0111, the decoder isconfigured for type A for the rest of the transmission.

According to an embodiment, if the first symbol is 0000, a second timeslot of same duration as the first one and consecutive thereto isdecoded for type A.

According to an embodiment:

-   -   if a second symbol corresponding to the second time slot is also        0000, the decoder is configured for the type-B modulation; and    -   otherwise, the decoder is configured for the type-15693        modulation.

According to an embodiment, if the first symbol is neither 0111 nor0000, the decoder is configured for the type-C modulation.

According to an embodiment, if the first symbol is 0101, the decoder isconfigured for the type-C modulation at 212 kbits per second.

According to an embodiment, if the first symbol is further differentfrom 0101, the decoder is configured for the type-C modulation at 424kbits per second.

Another embodiment provides a near-field receive device comprising theabove circuit.

The foregoing and other features and potential advantages will bediscussed in detail in the following non-limiting description ofspecific embodiments in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a simplified diagram of a system of the type to which theembodiments which will be described apply;

FIG. 2 is a block diagram of an embodiment of an NFC routerconfiguration system;

FIG. 3 is a simplified timing diagram illustrating an example ofmodulated signals received by an NFC router;

FIG. 4 shows timing diagrams illustrating initial phases ofcommunication according to different communication types capable ofbeing used by an NFC router operating in card mode; and

FIG. 5 is a simplified flowchart of an NFC router configuration mode.

DETAILED DESCRIPTION

The same elements have been designated with the same reference numeralsin the different drawings, where the timing diagrams have been drawn outof scale. For clarity, only those steps and elements which are useful tothe understanding of the described embodiments have been shown and willbe detailed. In particular, the circuits for generating communicationframes according to the different standards have not been detailed, thedescribed embodiments being compatible with usual standards. Further,the generation of polling requests by a read or read/write terminal hasnot been detailed either, the described embodiments being here againcompatible with usual terminals.

The embodiments which will be described aim at an NFC router operatingin card mode and at its configuring for a communication with a reader.

FIG. 1 is a simplified representation of an example of a communicationsystem of the type to which the embodiments which will be describedapply.

A mobile telecommunication device 1 (for example, a GSM-type mobiledevice) is capable of communicating with a network symbolized by anantenna 2. Device 1 is further equipped with a near-field communicationrouter 3 capable of communicating with a terminal 4 (TERMINAL) forgenerating a radio frequency field.

Most often, a device 1 equipped with an NFC router is capable ofoperating both in so-called reader mode and in so-called card mode. Inreader mode, device 1 and its NFC router 3 behave as a read and writeterminal of another near-field communication device. In card mode, themobile device operates as a contactless electromagnetic transponder orchip card to communicate with terminal 4. There exist many alternativetelecommunication devices equipped with an NFC router, but all use thesame principle: when operating in card mode and within the range of anear-field communication terminal, they wait for a request from thisterminal to respond thereto.

The embodiments which will be described hereinafter more specificallyrefer to devices integrating both near-field communication (NFC) andtelecommunication circuitry. The described solutions however apply toany near-field communication device capable of operating according toseveral modulation types or standards.

When such a device is within the range of a terminal, it successivelyswitches to the different modulation types with which it is capable ofoperating, to detect the type according to which the terminal sends itsrequest and to be able to start a near-field communication therewith.

In certain cases, the terminal itself is capable of operating accordingto different types. In this case, it starts by sending a requestaccording to a first communication or modulation type and then, in theabsence of any response from a transponder, switches to another type,and so on. On the terminal side, this operation carries on in a loop aslong as no response has been received from a transponder.

Such usual solutions take time before the communication can start.Further, the modulation type risks not being detected.

This problem becomes more of a concern with the development of NFCrouters capable of operating according to different modulation types andthe multiplicity of multistandard terminals.

The embodiments which will be described may take advantage of thespecificities of the most frequent near-field communication standards toshorten the time of detection of the modulation type and reducesituations where no type is detected.

Any transmission from a near-field communication terminal to atransponder (reference will be made hereinafter to a card) is performedin amplitude modulation. The difference between modulation types is dueto the coding of the amplitude modulation transmission to transmit thebits.

FIG. 2 is a simplified block diagram of an embodiment of a modulationtype selection device. The representation of FIG. 2 is simplified andfunctional.

The NFC router is assumed to comprise an analog front end 12 (AFE)equipped with means for receiving the radio frequency signals. In theexample of FIG. 2, analog front end 12 is further assumed to be equippedwith circuitry (symbolized by a signal Tx) enabling to transmit to theterminal. It is generally spoken of a retromodulation from thetransponder to the terminal. An output of front end 12 is sent to ademodulator/decoder 14 (DECOD) of the received signals. It for exampleis an amplitude demodulation circuit associated with a digital decoder.Decoder 14 provides the received signals (Rx) to the other mobiletelecommunication device circuits (not shown). According to theembodiment shown in FIG. 2, circuit 14 also delivers the demodulatedsignal to a block 16 (SELECT) for selecting the received modulation type(TYPE).

The function of decoder 14 is, from a modulation type with which it isinitially configured, to detect the real type of modulation of thesignal received from front end 12, to configure decoder 14 for the restof the transmission once the type has been selected by block 16.

As will be explained hereinafter in relation with FIG. 4, it is providedto use a decoding based on a so-called overcoded type-A modulation todetect the different modulation types that may be received.

In NFC routers, radio frequency communications are based on standardsrespecting a carrier frequency of approximately 13.56 MHz. Transmissionsfrom the terminal to the transponder are amplitude-modulated, mainlyaccording to four families of types, called type A, type B, type C, andtype 15693 (ISO standards 14443). The different types have differenttransmission speeds, carrier modulation indexes, and data codings.

The transmission speed of types A and B is 106 kbits/s, 212 kbits/s, 424kbits/s, or 848 kbits/s. The transmission speed of type C is 212 kbits/sor 424 kbits/s. The rate of type 15693 is 6.64 kbits per second or 26.48kbits/s.

The modulation index of type A is 100%. The modulation index of type Bis 10%. Type C has a modulation index ranging between 8 and 30%. Type15693 has a modulation index of 100% (type noted 15693-100) or 10% (type15693-10). Type 15693 at 6.64 kbits/s bears reference 256 (15693-100-256and 15693-10-256) and type 15693 at 26.48 kbits/s bears reference 4(15693-100-4 and 15693-10-4).

FIG. 3 illustrates, in a simplified timing diagram, a usual example ofamplitude modulation transmission of bits at states 0 and 1 with atype-A modulation. These timing diagrams show examples of the shape ofvoltage V recovered by front end 12. These signals are carried by acarrier at 13.56 MHz and are amplitude-modulated.

In the case of a terminal-to-transponder transmission considered hereinto detect the modulation type transmitted by the terminal on thetransponder side, the data bits are, in type A, coded according to theposition of a modulation-free interval I (or at a level lower than thehigh no-load level for other types such as type B) during a determinedperiod T representing a symbol. This modulation type is an ASK-typemodulation (amplitude shift keying). A bit 0 is decoded if pulse I is atthe beginning of a period T and a bit 1 is decoded if pulse I is not atthe beginning of period T. The duration of period T, and thus of asymbol, is approximately 9.44 microseconds. The duration of pulse Icorresponds to the duration of the symbol divided by 4.

The amplitude modulation is performed by lowering a high level sincenear-field communication systems basically are designed for transpondersextracting the power supply of the circuits that they comprise from thehigh-frequency field emitted by the terminal.

The embodiments which will be described may take advantage of the factthat, whatever the modulation type, a transmission from the terminal tothe transponder starts by an initial phase according to a specificcoding, but with symbols all having a duration of approximately 9.44microseconds (corresponding to a 106 kbits/s rate) independently fromthe modulation type.

An overcoding based on a time unit corresponding to the duration of asymbol (or type-A bit) divided by four, and thus to pulse I is defined.It is then provided to interpret this overcoding of four bits per symbolto discriminate the different modulation types. In other words, a symbolis divided into four elements and a state 0 or 1 is assigned to eachsymbol quarter according to its (relative) low or high level. Inpractice, this decoding is performed by a type-A demodulator todetermine the position of pulse I (FIG. 3), and thus the value of areceived bit. It is thus sufficient to interpret differently the valueof a type-A demodulated symbol.

FIG. 4 shows timing diagrams according to different modulation types toillustrate the selection mode performed in relation with FIG. 2. Thefirst timing diagram illustrates the shape of carrier SC approximatelyat 848 kHz (period of approximately 1.18 μs). The following timingdiagrams illustrate the respective shapes of the symbols present at astart of frame, respectively according to the following types:

-   -   C-424 (type C at 424 kbits/s): symbol not recognized;    -   C-212 (type C at 212 kbits/s): alternation of pulses        representing pulses I;    -   A: symbol representing a bit at state 0 in type A (FIG. 3);    -   B: 5 symbols at 0 followed by a symbol at 1;    -   15693: 1 half-symbol in the low state followed by several        half-symbols in the high state (4 in 15693-(100 or 10)-4 and 6        in 15693-(100 or 10)-256).

The type-A modulation is that where the start of frame (SOF) is theshortest, data DATA being transmitted after a single symbol at 0according to type A, that is a symbol having value 0111 according to theovercoding of four bits per symbol.

The frames, which may be of initialization frame type, illustrated inFIG. 4, are transmitted during relatively long time periods to leavetime for a transponder to detect the frame. For example:

-   -   a type-B frame represents 94 microseconds;    -   a type-C-424 frame represents 112 microseconds;    -   a type-C-212 frame represents 224 microseconds; and    -   a frame 15693 represents approximately 75 microseconds.

Waiting each time for a full frame in order for the terminal to considera lack of compatibility with the transponder before switching to anothertype of modulation takes time.

Further, applications in which near-field communications are usedgenerally are applications where a user brings his device close to theterminal and where transactions should be performed rapidly.

An embodiment uses one or two 9.44 μs durations representing thetransmission time of a type-A symbol, to determine the modulation typeused by the terminal during the sending of its start of frame.

FIG. 5 is a simplified flowchart of a selection mode implemented byselector 16 of FIG. 2 to determine the type of modulation transmitted bya terminal.

At the starting of the system (block 21, START), radio frequency frontend 12 is woken up by the receiving of a signal from a terminal andselector 16 initially configures decoder 14 to be able to decode atype-A modulation (block 22, CONFIG TYPE A). The no-load configurationof decoder 14 thus is type A.

Decoder 14 demodulates and decodes the received signal as if it was atype-A modulation and sends the received bits to selector 16. Thereceived bits are sent in parallel to the rest of the transpondercircuit but are not exploited for the time being. In particular, as longas selector 16 has not validated the modulation type by a signalintended for these circuits (a validation bit OK intended for the devicemicrocontroller), signal Rx is not used.

The selector waits (block 23, WAIT 4 BITS) for the reception of fourovercoded bits (or of a type-A symbol). This amounts to decoding, intype A, a 9.44-μs time slot, independently from the received signal andfrom the coding performed by the modulation type.

Once these four bits have been received and decoded, selector 16determines whether these bits correspond to a symbol of value 0111(block 24, 0111?). This amounts to detecting the presence of astart-of-frame symbol on a type-A modulation.

If the answer is positive (output Y of block 24), this means that theterminal is configured for the type-A modulation. Selector 16 validatesthe configuration type of decoder 14 (block 25, TYPE A) and theconfiguration process is ended (block 26, END).

If the answer is no (output N of block 24), selector 16 determineswhether the received symbol has value 0000 (block 27, 0000?). Such asymbol has no meaning in a type-A modulation. However, it enables todetermine whether the modulation is of type C or of type B or 15693.

If the symbol is 0000 (output Y of block 27), this means (see FIG. 4)either a type-B configuration or a type-15693 start of frame. Theequivalent of a next symbol in type A (block 28-1, WAIT 4 BITS), andthus a second time slot of approximately 9.44 μs, should then bedecoded.

Once this symbol has been received, selector 16 interprets it byquarters and compares the received symbol with value 0000 (block 29,0000?). If the symbol is 0000, this means a type-B modulation (block 30,TYPE B). Selector 16 then modifies the configuration of decoder 14 sothat it is configured on type B and the configuration is ended (block26). Two periods of 9.44 microseconds are thus sufficient to identifytype B.

If the result is negative (output N of block 29), this means a type15693 and selector 16 appropriately configures the decoder (block 31,TYPE 15693) and the configuration is ended (block 26). Here again, intwo periods of 9.44 microseconds, it has been possible to properlyconfigure the receiver.

If the interpretation of the first type-A symbol is neither 0111 nor0000 (output N of block 27), its value is compared with 0101 (block 28-20101?). Such a symbol here again has no meaning in a type-A modulation.However, it enables to determine whether the modulation is of type C at212 kbits (see the timing diagram of FIG. 4). Accordingly, if the symbolis 0101, the selector configures the decoder in type C 212 (block 32,TYPE C 212). If it is not, this means that the modulation is of type C424 (block 33, TYPE C 424).

The foregoing description shows that by interpreting at most twoconsecutive time slots having a duration corresponding to that of asymbol of the initialization frames (also corresponding to the durationof a symbol in the type-A modulation), one can configure the receiver byinterpreting the symbol as if it was overcoded on 4 bits.

It is thus no longer necessary to wait for the end of a frame, nor for aswitching of the terminal to another modulation type. As soon as it isproperly configured according to the method of FIG. 5, the device incard mode responds to the terminal by using the right type ofretromodulation, which is a function of the modulation type.

This method may be used either to configure a device in near field whilea terminal only transmits according to a modulation type, or to matchthe modulation of this near-field device with respect to a terminalscanning the different modulation types. In both cases, the devices arethen capable of communicating together.

Once the type has been identified by the selector, the mobiletelecommunication device is configured to send an acknowledgementmessage to the terminal. Receiving this response, the terminal knowsthat the transponder is capable of interpreting the modulation that ittransmits.

In a simplified embodiment, the above-described method only detects someof the modulation types.

For example, for a device only operating according to types A and C,only tests 24, 27, and 28-2 will be performed and, in case of a positiveoutcome of test 27, the device does not respond and waits for theterminal to switch to another modulation type.

According to another example, the device is only capable of operating intype A, in type B, or in type 15693. In this case, in the occurrence ofa failure of test 27, it is waited for the terminal to change modulationtype.

Further, the order of tests 24, 27, and 28-2 may be modified. Thediscussion of FIG. 5 however is an embodiment which facilitates morerapidly identifying type A.

Various embodiments have been described. Various alterations andmodifications will readily occur to those skilled in the art. Inparticular, the selection of the types detected by the implementation ofthese embodiments depends on the concerned mobile telecommunicationdevice, provided for it to be capable of decoding at least one type-Amodulation.

Further, the practical implementation of the described embodiments iswithin the abilities of those skilled in the art based on the functionalindications given hereabove. In particular, the interpretation of thetransmitted symbols may be performed by the digital processing circuitsusually present in a device comprising an NFC router. It will however beascertained to parameterize the receive front end and the decoder on aninterpretation of a signal duration approximately corresponding to 9.44microseconds.

Such alterations, modifications, and improvements are intended to bepart of this disclosure. Accordingly, the foregoing description is byway of example only and is not intended to be limiting.

What is claimed is:
 1. A device, comprising: demodulation and decodingcircuitry, which in operation, decodes received signals according to aselected modulation type of a plurality of modulation types; andmodulation-type selection circuitry, coupled to the demodulation anddecoding circuitry, wherein the modulation-type selection circuitry, inoperation, determines a modulation type of a received signal, thedetermining the modulation type of the received signal including:controlling the demodulation and decoding circuitry to decode thereceived signal as a type-A modulated signal for a first time slotcorresponding to a duration of a type-A symbol; when a result of thedecoding of the first time slot as a type-A modulated signal is 0111,selecting type-A modulation as the modulation type of the receivedsignal; and when the result of the decoding of the first time slot as atype-A modulated signal is 0101, selecting type-C modulation at 212kbits per second as the modulation type of the received signal.
 2. Thedevice of claim 1 wherein when the result of decoding the first timeslot as a type-A modulated signal is 0000, the modulation-type selectioncircuitry controls the demodulation and decoding circuitry to decode thereceived signal as a type-A modulated signal for a second time slotcorresponding to the duration and selects the modulation type of thereceived signal based on the result of the decoding of the second timeslot as a type-A modulated signal.
 3. The device of claim 2 wherein:when the result of the decoding of the second time slot as a type-Amodulated signal is 0000, the modulation-type selection circuitryselects type-B modulation as the modulation type of the received signal;and when the result of the decoding of the second time slot as a type-Amodulated signal is not 0000, the modulation-type selection circuitryselects type-15693 modulation as the modulation type of the receivedsignal.
 4. The device of claim 1 wherein when the result of the decodingof the first time slot as a type-A modulated signal is not included in aset of results {0000, 0111, 0101}, the modulation-type selectioncircuitry selects type-C modulation at 424 kbits per second as themodulation type of the received signal.
 5. The device of claim 1 whereinwhen the result of the decoding of the first time slot as a type-Amodulated signal is not included in a set of results {0111, 0101}, themodulation-type selection circuitry selects type-C modulation at 424kbits per second as the modulation type of the received signal.
 6. Thedevice of claim 1 wherein the modulation-type selection circuitryenables an output of the demodulation and decoding circuitry afterselecting the modulation type of the received signal.
 7. A system,comprising: analog-front-end circuitry; and digital-signal-processingcircuitry coupled to the analog-front-end circuitry, wherein thedigital-signal-processing circuitry, in operation, determines amodulation type of a received signal, the determining the modulationtype of the received signal including: decoding the received signal as atype-A modulated signal for a first time slot corresponding to aduration of a type-A symbol; when a result of the decoding of the firsttime slot as a type-A modulated signal is 0111, selecting type-Amodulation as the modulation type of the received signal; and when theresult of the decoding of the first time slot as a type-A modulatedsignal is 0101, selecting type-C modulation at 212 kbits per second asthe modulation type of the received signal; and decoding the receivedsignal using the selected modulation type of the received signal.
 8. Thesystem of claim 7 wherein when the result of decoding the first timeslot as a type-A modulated signal is 0000, the digital-signal-processingcircuitry decodes the received signal as a type-A modulated signal for asecond time slot corresponding to the duration and selects themodulation type of the received signal based on the result of thedecoding of the second time slot as a type-A modulated signal.
 9. Thesystem of claim 8 wherein: when the result of the decoding of the secondtime slot as a type-A modulated signal is 0000, thedigital-signal-processing circuitry selects type-B modulation as themodulation type of the received signal; and when the result of thedecoding of the second time slot as a type-A modulated signal is not0000, the digital-signal-processing circuitry selects type-15693modulation as the modulation type of the received signal.
 10. The systemof claim 7 wherein when the result of the decoding of the first timeslot as a type-A modulated signal is not included in a set of results{0000, 0111, 0101}, the digital-signal-processing circuitry selectstype-C modulation at 424 kbits per second as the modulation type of thereceived signal.
 11. The system of claim 7 wherein when the result ofthe decoding of the first time slot as a type-A modulated signal is notincluded in a set of results {0111, 0101}, the digital-signal-processingcircuitry selects type-C modulation at 424 kbits per second as themodulation type of the received signal.
 12. The system of claim 7wherein the digital-signal-processing circuitry enables a decoded signaloutput after selecting the modulation type of the received signal. 13.The system of claim 7, comprising a near-field communication routerincluding the analog-front-end circuitry and thedigital-signal-processing circuitry, wherein the analog front end, inoperation, receives and transmits radio frequency signals.
 14. Anon-transitory computer-readable medium whose contents configure anear-field communication router to perform a method, the methodcomprising: determining a modulation type of a received signal, thedetermining the modulation type including: decoding the received signalas a type-A modulated signal for a first time slot corresponding to aduration of a type-A symbol; when a result of the decoding of the firsttime slot as a type-A modulated signal is 0111, selecting type-Amodulation as the modulation type of the received signal; and when theresult of the decoding of the first time slot as a type-A modulatedsignal is 0101, selecting type-C modulation at 212 kbits per second asthe modulation type of the received signal; and decoding the receivedsignal using the selected modulation type of the received signal. 15.The medium of claim 14 wherein when the result of decoding the firsttime slot as a type-A modulated signal is 0000, the method comprisesdecoding the received signal as a type-A modulated signal for a secondtime slot corresponding to the duration and selecting the modulationtype of the received signal based on the result of the decoding of thesecond time slot as a type-A modulated signal.
 16. The medium of claim15 wherein the method comprises: when the result of the decoding of thesecond time slot as a type-A modulated signal is 0000, selecting type-Bmodulation as the modulation type of the received signal; and when theresult of the decoding of the second time slot as a type-A modulatedsignal is not 0000, selecting type-15693 modulation as the modulationtype of the received signal.
 17. The medium of claim 14 wherein themethod comprises: when the result of the decoding of the first time slotas a type-A modulated signal is not included in a set of results {0000,0111, 0101}, selecting type-C modulation at 424 kbits per second as themodulation type of the received signal.
 18. The medium of claim 14wherein the method comprises: enabling a decoded signal output afterselecting the modulation type of the received signal.
 19. A method,comprising: determining a modulation type of a received signal usingnear-field communication routing circuitry, the determining themodulation type including: decoding, using the near-field communicationrouting circuitry, the received signal as a type-A modulated signal fora first time slot corresponding to a duration of a type-A symbol;responding to a result of 0111 of the decoding of the first time slot asa type-A modulated signal, by selecting, by the near-field communicationrouting circuitry, type-A modulation as the modulation type of thereceived signal; and responding to a result of 0101 of the decoding ofthe first time slot as a type-A modulated signal, by selecting, by thenear-field communication routing circuitry, type-C modulation at 212kbits per second as the modulation type of the received signal; anddecoding, by the near-field communication routing circuitry, thereceived signal using the selected modulation type of the receivedsignal.
 20. The method of claim 19, comprising: when the result ofdecoding the first time slot as a type-A modulated signal is 0000,decoding, by the near-field communication routing circuitry, thereceived signal as a type-A modulated signal for a second time slotcorresponding to the duration and selecting, by the near-fieldcommunication routing circuitry, the modulation type of the receivedsignal based on the result of the decoding of the second time slot as atype-A modulated signal.
 21. The method of claim 20, comprising: whenthe result of the decoding of the second time slot as a type-A modulatedsignal is 0000, selecting type-B modulation as the modulation type ofthe received signal; and when the result of the decoding of the secondtime slot as a type-A modulated signal is not 0000, selecting type-15693modulation as the modulation type of the received signal.
 22. The methodof claim 19, comprising: when the result of the decoding of the firsttime slot as a type-A modulated signal is not included in a set ofresults {0000, 0111, 0101}, selecting, by the near-field communicationrouting circuitry, type-C modulation at 424 kbits per second as themodulation type of the received signal.
 23. The method of claim 19,comprising: enabling, by the near-field communication routing circuitry,a decoded signal output after selecting the modulation type of thereceived signal.